About Me

Contributor to GNU Project
- GNU Emacs, Guile, glibc, GCC
- GPLv3, GNU Privacy Guard
- Japanese Translation Team
Contributor to Linux: PLIP, SuperH, M32R
Debian Developer: Golly
Chair of FSIJ

Distro and Crypto Token

Distribution developers care about integrity of distribution
- GnuPG is our friend
Where to put my GPG keys?
- OpenPGP card is great
- but card reader (possibly big) is not my friend
- Crypto Stick is great too

What’s Gnuk?

Free Software implementation of Cryptographic Token
Supports OpenPGP card protocol version 2
Runs on STM32 processor
Supports RSA 2048-bit

Named after NUK®

My son used to be with his NUK®, always, everywhere
I wish Gnuk Token can be a soother for GnuPG user

NUK® is a registered trademark owend by MAPA GmbH, Germany.

Cryptographic Token?

Stores your Secret Keys
Performs security operations on the device
- Digital signature
- Authentication
- Decryption
No direct access to Secret Keys

How useful?

Can bring secret keys securely
On the go, you can do:
- Make digital signature
- Authenticate yourself
- Read encrypted mail

GNU Privacy Guard (GnuPG)

Privacy Tool by Cryptography

Conforms to OpenPGP standard
Usage:
- Digital Signature
- Encryption/Decryption
- Authentication
Supports "OpenPGP card"

OpenPGP card

Smartcard to put GnuPG keys
Follows OpenPGP protocol standard
Features of v2.0:
- RSA 1024-bit, 2048-bit, 3072-bit
- Three keys: Sign, Decrypt, Auth
- Key generation on the card
- RSA accelerator

OpenPGP card Applications

GnuPG
OpenSSH → gpg-agent
TLS/SSL Client authentication
- Scute (Network Security Service)
PAM
- Poldi

Gnuk (Since Sep. 2010)

Focus on software
CPU choice: STM32 (ARM Cortex-M3)
Target boards:
- Olimex STM32-H103
- STM32 part of STM8S Discovery Kit
- Original board: FST-01

Gnuk Approach

OpenPGP card protocol, not PKCS#11
- PKCS#11 can be emulated on top of OpenPGP card protocol
Minimum CCID implementation
Short APDU level exchange

Implementation

Kernel by ChibiOS/RT
Crypto by PolarSSL (RSA, AES, SHA1)
Implements:
- CCID/ICCD Protocol
- OpenPGP card protocol / ISO 7816
- Flash ROM management

As of Gnuk 0.17

12 header files in src/
20 implementation files in src/
About 9000 lines of C code

Gnuk Licence

GNU GPL v3 (and later)

How fast?

RSA 2048-bit digital signing
- 1.48sec (version 0.13 or later)
Useful for GnuPG users
Useful for OpenSSH users

Limitations of Gnuk

Using normal processor
- Tamper Resistance?
  - Flash Read Protection only
- No RSA accelerator
  - Not that fast
  - Up to 2048-bit

Good points of Gnuk

Free Software
Develop/test new things
- New protocol enhancement
- New encryption algorithm
- New PIN input for authentication

Current Status of Gnuk (1)

GnuPG: works well
OpenSSH: works well
Firefox + Scute: Tested on CAcert.org

Current Status of Gnuk (2)

Not supported:
- Secure Messaging support
  - USB sniffer can see passphrase
- Key generation
- Overriding key import

Known Problems

OpenPGP card is not portable .gnupg
- Just secret keys
  - No pubring
  - No trustdb

Supported Boards

Olimex STM32-H103
Flying Stone Tiny 01 (FST-01)
STM32 part of STM8S Discovery Kit
CQ STARM, STBee, STBee Mini

Gnuk Development

Web page:
- http://www.fsij.org/gnuk/
Git Repository:
- http://www.gniibe.org/gitweb?p=gnuk.git

Gnuk Development Requirements

GNU Toolchain for ARM
- summon-arm-toolchain
Python (PyUSB, PySCard)
OpenOCD
Git

Gnuk Host Requirements

Tested on Debian, Gentoo
- GnuPG (>= 1.4.11, >=2.0.14)
- pcscd (>= 1.5.5)
- libccid (>= 1.3.11)
Tested a bit on Windows

Steps of building Gnuk Token

Build gnuk.elf
Write gnuk.elf to STM32
Serial number setup (optional)
Personalize Gnuk Token
Import keys to Gnuk Token

Using Gnuk Token for SSH authentication

Don’t run seahorse, but gpg-agent
Don’t run ssh-agent, but gpg-agent
Don’t run gnome-keyring

.gnupg/gpg.conf

  use-agent

.gnupg/gpg-agent.conf

  enable-ssh-support

STM8S Discovery Kit (1)

Development Kit for STM8S
Use STM32F103 for USB dongle
750 JPY
Can be: DIY Gnuk Token

STM8S Discovery Kit (2)

STM32 part

DIY JTAG Debugger

It takes only 2000 JPY, using FTDI 2232 module.

$Image372.jpg$

STBee Mini with pinpad

Topvalu Mint tablet case

Hair pin case

FST-01 PCB

PCB design by KiCAD
Distributed under CC BY-SA 3.0

FST-01 Engineering Prototype

STM32F103TB, SPI Flash memory
USB Terminator, LDO Regulator
12MHz XTAL, LED

Future Work

ECC P256 support (quite fast)
configure time USB vendor ID, product ID setup
Support data other than secret keys
- Towards portable .gnupg environment

Acknowledgments

Werner Koch for GnuPG
Achim Pietig for OpenPGP card specification
Giovanni Di Sirio for ChibiOS/RT
Contributors of Gnuk, including:
- Hironobu SUZUKI
- Kaz Kojima
- MATSUU Takuto
- NAGAMI Takeshi

References (1)

[GNUPG] GNU Privacy Guard, http://www.gnupg.org/
[CHIBI] ChibiOS/RT, http://chibios.sourceforge.net/
[POLAR] PolarSSL, http://polarssl.org/
[CARD20] Achim Pietig, "Functional Specification of the OpenPGP application on ISO Smart Card Operating Systems (Version 2.0.1)", 2009-04-22.

References (2)

[CCID] USB Implementers Forum, "Specification for Integrated Circuit(s) Cards Interface Devices", Revision 1.1, 2005-04-22.
[ICCD] USB Implementers Forum, "Specification for USB Integrated Circuit(s) Card Devices", Revision 1.0, 2005-04-22.
[ISO7816] ISO/IEC 7816-4:2005, "Identification cards — Integrated circuit cards — Part 4: Organization, security and commands for interchange", 2005.
[RFC4880] J. Callas, L. Donnerhacke, H. Finney, D. Shaw, R. Thayer, "OpenPGP Message Format", November 2007.

References (3)

[FSIJ2009] Niibe Yutaka, "FSIJ USB Token for GnuPG", Japan Linux Symposium, Tokyo, 2009-10-21.
[PKCS11] RSA Laboratories, "PKCS #11 v2.20: Cryptographic Token Interface Standard", 2004-06-28.
[PKCS15] RSA Laboratories, "PKCS #15 v1.1: Cryptographic Token Information Syntax Standard", 2000-06-06.
[FIPS201] Federal Information Processing Standard 201-1, "Personal Identity Verification (PIV) of Federal Employees and Contractors", March 2006.
[SP800-78] NIST Special Publication 800-78-3, "Cryptographic Algorithms and Key Sizes for PIV", December 2010.

Gnuk — An OpenPGP USB Token Implementation

About Me

Distro and Crypto Token

What’s Gnuk?

Named after NUK®

Cryptographic Token?

How useful?

GNU Privacy Guard (GnuPG)

OpenPGP card

OpenPGP card Applications

Gnuk (Since Sep. 2010)

Gnuk Approach

Implementation

As of Gnuk 0.17

Gnuk Licence

How fast?

Limitations of Gnuk

Good points of Gnuk

Current Status of Gnuk (1)

Current Status of Gnuk (2)

Known Problems

Supported Boards

Gnuk Development

Gnuk Development Requirements

Gnuk Host Requirements

Steps of building Gnuk Token

Using Gnuk Token for SSH authentication

STM8S Discovery Kit (1)

STM8S Discovery Kit (2)

STM32 part

DIY JTAG Debugger

STBee Mini with pinpad

Topvalu Mint tablet case

Hair pin case

FST-01 PCB

FST-01 Engineering Prototype

Future Work

Acknowledgments

References (1)

References (2)

References (3)

Gnuk Stickers